Methods for the preparation of improved faujasite compositions

ABSTRACT

Faujasite-type zeolites of high SiO2/Al2O3 mole ratios are prepared utilizing a two-step process employing relatively abundant starting materials. The process includes an intermediate acidification step followed by a second holding period during which crystallization occurs.

- United States Patent [191 Maness Dec.'3,1974

[ METHODS FOR THE PREPARATION OF llMPROVED FAUJASITE COMPOSITIONS Related US. Application Data [62] Division of Ser. No. 169,069, Aug 4, 1971, Pat. No.

[52] US. Cl 423/329, 423/118, 423/328, 252/455 Z [51] Int. Cl. COlb 33/28, COlb 33/26 [58] Field of Search 423/328, 329, 330, 118; 252/455 Z [56] 7 References Cited UNITED STATES PATENTS 3,037,843 6/1962 Mason .1 423/118 3,101,251 8/1963 Howell 423/118 3,130,007 4/1964 Breck....'. 423/328 3,374,182 3/1968 Young 423/328 X 3,695,837 10/1972 Sunderland et a1 423/329 3,733,390 5/1973 Robson 423/118 Primary Examiner-Edward Stern Attorney, Agent, or FirmA. H. Krumhonz; Roy J. Ott

[ 5 7 ABSTRACT Faujasite-type zeolites of high SiOJAl O mole ratios are prepared utilizing a two-step process employing relatively abundant starting materials. The process includes an intermediate acidification step followed by a second holding period during which crystallization occurs.

6 Claims, N0 Drawings METHODS FOR THE PREPARATION OF IMPROVED FAUJASITE COMPOSITIONS This is a division, of application Ser. No. 169,069 filed Aug. 4, 1971 now US. Pat. No. 3,701,629 issued Oct. 31, 1972.

FIELD OF THE INVENTION The present invention relates to a novel method for the preparation of crystalline aluminosilicate zeolites suitable for use in various hydrocarbon adsorption and- /or conversion processes. More particularly, the present invention relates to the preparation of crystalline aluminosilicate zeolites of the faujasite-type, having a silica to alumina mole ratio of at least about 4.0.

Another embodiment of the present invention relates to the use of these zeolite materials in various hydrocarbon adsorption and/or conversion processes.

BACKGROUND OF THE INVENTION Various processes for the preparation of crystalline aluminosilicate zeolites from silica and aluminumcontaining materials have heretofore been proposed. Thus, for example, crystalline aluminosilicate zeolites having a silica to alumina mole ratio of about 2.5 to about 3.5 can be readily prepared by methods which in general involve digesting aqueous solutions of sodium silicate and sodium aluminate at elevated temperatures. The raw materials required for manufacturing these low-silica, crystalline aluminosilicate zeolites are relatively inexpensive. Previous attempts to prepare high-silica, crystalline aluminosilicate zeolites, i.e. having silica to alumina mole ratios greater than about 4.0, directly from inexpensive sources of silica, e.g. sodium silicate solutions, have however met with difficulty, see US. Pat. No.:3,227,660, column 2, and 3,484,194. In addition, such zeolites have recently been prepared from other crystalline aluminosilicate zeolites, as is disclosed in recently filed Ser. No. 104,745, to Harry E. Robson, quite successfully, but such processes have not always resulted in the preparation of crystalline aluminosilicate zeolites having as high'a silica to alumina mole ratio as is desirable.

One of the well known methods'for the manufacture of high-silica crystalline aluminosilicate zeolites requires a silica hydrosol as the major starting material. These hydrosols, as exemplified by the commercial Ludox,are prepared by extensive ion exchanging of sodium silicate solutions. This procedure is quite expensive and thus the resulting silica hydrosols are several times as costly as sodium silicate, on an equivalent SiO basis. Thus, for example, in US. Pat. No. 3,130,007, when it was desired to prepare a crystalline aluminosilicate having a silica to alumina mole ratio greater than 3.9, silica sources such as expensive aqueous colloidal silica sols were necessary as the major sources of silica.

Another method for producing crystalline aluminosilicate zeolites isdescribed in US. Pat. No. 3,227,660. In this process, the patentees use sodium silicate as the major starting material, but need to convert it to a silica hydrogel by conventional methods, i.e. by acidifyinga sodium silicate solution to a pH below about 10, and washing and partially drying the resulting hydrogel. Thus, in order to obtain high silica to alumina mole ratio products, the patentees found it necessary to use an added peptizing step wherein the silica hydrogel was partially peptized in an aqueous sodium hydroxide solution at an ambient temperature of, e.'g., about to 50C., for up to about 3 hours. The final product contained only about 35 to by weight of the desired high-silica, crystalline aluminosilicate zeolite.

In addition, U.S. Ser. No. 104,745 referred to hereinbefore, recently disclosed a valuable and inexpensive method for preparing such crystalline aluminosilicate zeolites utilizing other crystalline: aluminosilicate zeolites as starting materials. This process utilizes alkali metal hydroxide solutions to convert the initial crystalline aluminosilicate zeolite materials, but is limited in the silica/alumina mole ratio of the product obtainable.

It is thus quite apparent that all these prior art processes demonstrate the difficulty encountered in preparing crystalline aluminosilicate zeolites of high purity and having silica to alumina mole ratios greater than about 4.0 inexpensively and in high yields.

SUMMARY OF THE INVENTION In accordance with the present invention, it has been discovered that crystalline aluminosilicate zeolites of the faujasite type, and having silica to alumina mole ratios of at least about 4.0, can be prepared by the acidification of the zeolite-forming reaction mixture at a specific time during the zeolite preparation procedure. Further in accordance with the present invention, these high-silica crystalline aluminosilicate zeolite products may be utilized in various hydrocarbon conversion pro cesses.

DETAILED DESCRIPTION The crystalline zeolite preparation procedure of the present invention primarilyconsists of preparing a reaction mixture containing a source of silica, a source of alumina, a source of alkali metal oxide, and water, and may also include a promoter such as sodium chloride. The reaction mixture is then generally put into solution and thoroughly mixed at ambient temperature, e.g. 25C, and heated to a temperature generally of from about to about 150C. Pressure must be applied at temperatures about 100C. to prevent substantial loss of water from the reaction mixture. In the standard procedur'es employing such reaction mixtures for preparing crystalline aluminosilicate zeolites,th'ese c0nventional mixtures have then generally been held at these high temperatures for a sufficient time to form a crystallized product. In the present invention, however, during this initial holding period the reaction mixture is acidified to a Nap/S10 ratio of from 0.25 to about 0.40, preferably 0.32 to 0.38, and most preferably 0.34 to 0.36. The reaction mixture is then again held at the above noted temperatures during a second holding period for a further time inorder to produce the crystalline zeolitic product. I i I In such procedures where the major source of silica in the reaction mixture is sodium silicate, silica gel or silicic acid, the reaction mixture will have a'composition expressedin terms of oxide-mole ratios falling within the following ranges:

A B C Naplsio, 0.6 to 1.0 1.5 to 1.7 1.9 to 2.1 SiO /Al O 8 to 3O 10 to 30 about l0 "go/N820 12 to 20 to 90 40 to 90 And where a promoter such as NaCl is added to this reaction mixture, the ratio of NaCl to A1 0 in the mixabout 1% hours, at which time the solution is acidified to a Na O/SiO ratio of from 0.25 to about 0.40, preferably from 0.32 to 0.38 and most preferably from 0.34 to 0.36. This composition is then further maintained at Clinoptilolite from Mt. Hector, California 4 chracteristics of this material appears in the American Mineralogist, Vol. 45, 1960, at pages 351-369, in an Article by F. A. Mumpton, which includes a review of the X-ray diffraction pattern of a clinoptilolite sample from Mt. Hector, California.

a temperature in the range of from about 90 to about 5 In Order to P p this faujasite Product according 110C. for a period of from about 40 to ab 231 to the present invention,-utilizing the clinoptilolite as a hours, preferably 64 to 159 hours, and most preferably starting material, an initial reaction mixture is prepared 90 to 110 hours. by blending the clinoptilolite with an alkali metal hy- In the process of the present invention wherein the droxide in aqueous solution, such that the ratio of sources of both silica and alumina comprise an initial l-hO/zeolite employed will be from between about 0.3 crystalline aluminosilicate zeolite, and the initial reacg./g. to about 2.0 g./g., preferably from 0.5 to 1.5 g./g. tion mixture includes an aqueous alkali metal hydroxand most preferably from 0.9 to 1.1 g./g. The alkali ide solution, generally utilizing high concentrations of metal hydroxide concentration will be such as to comalkali solution, preferably from 10 to 50% NaOH, and prise from 10 to 50% NaOH and preferably from to most preferably from 20 to 35% NaOH, this initial re- 35% NaOH, thus giving a mole ratio of Na O/SiO in action mixture is maintained at from about to terms of mole ratios of oxides, in the initial reaction 150C., preferably 80 to 130C, and most preferably mixture of from 0.20 to about 1.2, preferably from 0.40 from 90 to l 10C., for an initial period of from 0.5 to to about 0.50. about 2.5 hours, preferably from 1 to 2 hours, and most 20 Th s reaction mixture Will then be heated to a tempreferably about 1.5 hours, at which time this solution perature of from 90 to 1 10C., and maintained at that is acidified to a Na O/SiO mole ratio of from 0.30 to temperature for a period of from 0.5 to 2.5 hours, prefabout 0.45, preferably from 0.32 to 0.38, and most erably l to 2 hours. preferably from 0.34 to 0.36. This solution is then addih tu l t be a i ifiedby the addition of tionally maintained at similar temperatures for a fur- 25 an acid, Such as 10 Provide a reaction miXtllre ther period of from 8 to 40 hours, preferably from 10 g a z z mole ratio of from 030 to ab0l1t0-45, to 24 hours, and most preferably from 15 to 17 hours, pr f ly from 0.34 to 0.36 an most p ferably of until the final crystallized product i f m d, about 0.35. This reaction mixture will then be main- This product, preferably being of the faujasite type, tained at a temperature of from 90 to l 10C., for a pewill have a SiO /Al O mole ratio greater than about 4, fiod of from 15 to 17 hours, h Producing a y preferably from about 4,2 to about 45, and most pref. llZCd faujasite-type crystalline aluminosilicate zeolite erably greater than about 4.9. having a SiO /Al O mole ratio greater than about 4, The acidification step previously described will gen- Preferably from to and thus a unit Cell Size less erally be carried out by the addition of an inorganic than about 24-80 Angstromsi and Preferably from acid to the reaction mixture, preferably acids such as 7 to 2458 A'ngstl'ornsi HCLHNOs, HBr and HCN, and most f rabl an The following 'Examples are representative of the inorganic acid such as HCl. processes of the present e t DESCRIPTION or THE PREFERRED EXAMPLE 1 EMBODIMENT 40 In order to further demonstrate the applicability of in an extremely important application of the present the present process to the preparation of faujasite from invention, the silica and alumina in the initial reaction the initial crystalline aluminosilicate zeolite clinoptilomixture are supplied by the initial crystalline alumino lite, several runs were carried out with varying degrees silicate zeolite clinoptilolite, one of the most abundant of acidification according to the present process. The naturally-occurring zeolites, and treatment according data obtained are contained in Table 1. In each of these to the process of the present invention results in the runs, initially 10 grams of clinoptilolite was mixed well synthesis of a v faujasite-type produce having a with 7 mls. of water and 6 grams of wt. percent silica/alumina mole ratio greater. thanabout 4, thus NaOH solution. This initial reaction mixture was then having a unit cell size below about 24.80 Angstroms. placed in a 4 ounce bottle, capped, and immersed in a Clinoptilolite is an extremely abundant natural crys- 50 100C. oil bath. The bottle was withdrawn from the tallinealuminosilicate zeolite whichhas not been found bath and cooled to room temperature prior to acidifiuseful for purposes of the adsorption or catalysis of hycation, and then re-capped and returned to the oil bath drocarbons heretofore. The reason for this is the very for the second holding period. Also in these runs, acidilow surface area of this material, and its concomitant fication was carried out after the initial holding period lack of adsorptive capacity, irrespective of its high sil- 0f 1% hours, and after acidification, a second holding ica to alumina molar ratio of about 1 l. A review of the period 0f 16 hours was employed.

TABLE 1 Na,0/ (Initial) SiO Products Na O/ Added After Acidi- Crystal- Unit Cell SiO I Initial Zeolite SiO, Acid fication Faujasite linity 7; Size A A1203 1) Clinoptilolite 0.47 None Yes 102 24.80 3.9 2 do. 047- 1.30 mls. of 0.45 Yes 99 24.768 4.19

12N HCI 3 do. 0.47 2.28 mls. of 0.35 Yes 24.704 4.69

. 12N HCI 4) do. 047 3.25 mls. of 0.3 Yes 15 Too weak To measure 12N HCl EXAMPLE 2 The general procedure employed in these runs for the formation of the initial reaction mixture included the use of 93.6 grams of AI O -3I-I O as the source of alumina, l,23l grains of a sodium silicate solution as the source of silica, 140 grams of NaOl-l, 50 grams of NaCl and 140 grams of water.

The data contained in Table 3 was obtained after an initial holding period of two hours, at 100C. Run No. 11, i.e., with no acidification asper the present inven- 10 tion, was carried out utilizing a mole ratio of Na O/SiO of 0.6, which is the lowest such ratio taught by Breck in U.S. Pat. No. 3,130,007 (see column 3, line 30).

TABLE 2 I Initial Na- O/ Products (Initial) Holding SiO, Unit Initial Na,0/ Added Period at After Acidi- Crystal- Cell SiO OI Zeolite SiO Acid IC.,Hrs. fication Faujasite linity 70 Size A A1 0 5) Clinoptilo- 0.47 None Yes I02 24.80 3.9

lite 6) do. 0.47 2.28 mls. l 0.35 Yes 47 24.708 4.66

l2N HC] 7) do. 0.47 2.28 mls. 1% 0.35 Yes 90 24.704 4.69

V l2N HCI 8) do. 0.47 2.28 mls. 2 0.35 Yes 36 24.678 4.82

12N HCI 9) do. 0.47 2.28 mls. 2% 0.35 Yes 23 Too weak to measure I2N HCI do. 0.47 2.28 mls. 3 0.35 Yes Too weak to measure l2N HCI Clinoptilolite from Mt. Hector, California TABLE 3 Nap/sic, Products (Initial) After Acidi Crystal- Unit Cell SiO,/ Na O/SiO Added Acid fication Faujasite linity, Size, A A1 0 1 l) 0.6 None Yes 200 24.97 3.0

2) 0.6 l9 mls 0.35 Yes 74 24.704 469 l2N HCI l3) 0.6 25 mls. 0.30 Yes 34 Tooweak to measure 12N HCI l4) 0.6 27 mls. 0.25 Yes 18 Too weak to measure I2N HCI EXAMPLE 3 EXAMPLE 4 In order to further demonstrate the scope of the present invention, several runs were carried out in which a faujasite-type zeolite product was prepared using sodium silicate solution as the source of silica, as perD.

In order to determine the optimumlength of time for the initial holding period, i.e., prior to acidification, several additional runs of varying initial holding periods were carried out in a manner similar to that described in Example. 3, and the'results obtained are contained in w. Breck in US. Pat. No. 3,130,007. Table 4.

TABLE 4 Initial Na olsio Holding Period After Products (Initial) Added at I00C.. Acidi- Crystal- Unit Cell SIOz/ Na,O/Si0 Acid Hrs. fication Faujasite linity Size, A A1 0 IS) 0.60 I9 mls. 0 035 Yes 5 Too weak to measure l2N HCI l6) 0.60 19 mls. I 0.35 Yes 24 Too weak to measure I2N HCI 17) 0.60 l9 mls. 2 0.35 Yes 24.755 4:29

12N HCI 4 I8) 0.60 19 mls. 3 0.35 Yes 57 24.759 4.26

l2N HCI 19) 0.60 l9 mls. 4 0.35 Yes 57 24.700 4.72

-I2N HCI 20) 0.60 l9 mls. 5 0.35 Yes I9 24.671 4.96

IZN HCI 21). 0.60 19 mls. 21 /4 0.35 Yes I98 24.979 3.0

EXAMPLE 5 In order to further demonstrate the scope of the present invention, several additional runs similar to those shown in Examples 3 and 4 were carried out, but at a 8 mixture at a temperature in the range of from about 25 to 150C. for an initial holding period of from 0.5 to 2.5 hours, acidifying and thereby reducing the Na O/SiO mole ratio of said reaction mixture so that the Na O/- constant intial holding period, at 100C, for two hours, 5 Q-z P f ratio is Within f g of from to and at varying second holding periods, The r ult f maintaining said reaction mlxturefor a second holding these runs are contained i Table perlod of from 8 to 40 hours, and recovering a crystal-v TABLE 5 Na O/SiO Second Products (initial) Added After Acidi- Holding Crystal- Unit Cell SiO Na O/SiO Acid fication Period, Hrs. Faujasite linity, Size, A A1 0; 22 0.60 19 mls. 0:35 40 Yes 90 24.755 4.29

' l2N HCI 23 0.60 l9 mls. 0.35 64 Yes 74 24.704 4.69

l2N HCl 24 0.60 19 mls. 0.35 In Yes 90 24.666 4.99

l2N HCl 25 0.60 19 mls. 0.35 159 Yes 112 24.653 5.09

l2N HCl 26) 0.60 19 mls. 0.35 231 Yes 56 24.909 3.09

l2N HCl Obviously, many modifications and variations of this V lized product having a silica/alumina mole ratio greater invention may be made without departing from the es- 225 than about 4. sence and scope thereof, and only such limitations 2. The method of claim 1 wherein the sodium Na- O/- should be applied as are indicated from the appended SiO mole ratio is reduced by acidification to a level claims. within the range of 0.32 to 0.38.

What i claimed i 3. The method of claim 1 wherein said alkali metal 1. A method for preparing a faujasite-type zeolite 30 Yd Xid comprises NaOH. from clinoptilolite crystalline aluminosilicate zeolite T e me od of Claim 1 wherein said initial reaction which comprises preparing an aqueous reaction mixmixture iS maintained at a temperature Of from 90 t0 ture containing said clinoptilolite crystalline aluminosilicate zeolite, alkali :metal hydroxide and water such The method O Claim 1 wherein Said initial holding that the ratio of water/zeolite in said mixture will be P 5 m 1 t0 2 hours. f b t about 0,3 t b t 20 d h 6. The method of claim 1 wherein said acidification mole ratio of Na O/SiO in said mixture will be from results i a mole ratiO 0f z z of from 0.34 o about 0.40to about 0.50, maintaining said reaction 

1. A METHOD FOR PREPARING A FAUJASITE-TYPE ZEOLITE FROM CLINOPTILOLITE CRYSTALLINE ALUMINOSILICATE ZEOLUTE WHICH COMPRISES PREPARING AN AQUEOUS REACTION MIXTURE CONTAINING SAID CLINOPTILOLITE CRYSTALLINE ALUMINOSILICATE ZEOLITE, ALKALI METAL HYDROXIDE AND WATER SUCH THAT THE RATIO OF WATER/ZEOLITE IN SAID MIXTURE WILL BE FORMED BETWEEN ABOUT 0.3 G./G. TO ABOUT 2.0 G./G. AND THE MOLE RAIO OF NA2O/SIO2 IN SAID MIXTURE WILL BE FROM ABOUT 0.40 TO ABOUT 0.50, MAINTAINING SAID REACTION MIXTURE AT A TEMPERATURE IN THE RANGE OF FROM ABOUT 25* TO 150*C. FOR AN INITIAL HOLDING PERIOD OF FROM 0.5 TO 2.5 HOURS, ACIDIFYING AND THEREBY REDUCING THE NA2O/SIO2 MOLE RAIO OF SAID REACTION MIXTURE SO THAT THE NA2/SIO2 MOLE RATIO IS WITHIN THE RANGE OF FROM 0.30 TO 0.45, MAINTANING SAID REACTION MIXTURE FOR A SECOND HOLDING PERIOD OF FROM 8 TO 40 HOURS, AND RECOVERING A CRYSTALLIZED PRODUCT HAVING A SILICA/ALUMINA MOLE RATIO GREATER THAN ABOUT
 4. 2. The method of claim 1 wherein the sodium Na2O/SiO2 mole ratio is reduced by acidification to a level within the range of 0.32 to 0.38.
 3. The method of claim 1 wherein said alkali metal hydroxide comprises NaOH.
 4. The method of claim 1 wherein said initial reaction mixture is maintained at a temperature of from 90 to 110*C.
 5. The method of claim 1 wherein said initial holding period is from 1 to 2 hours.
 6. The method of claim 1 wherein said acidification results in a mole ratio of Na2O/SiO2 of from 0.34 to 0.36. 